The Chapuis action, twin lumps, trigger plate, is pretty similar to the Fabarm Classis and Beta action, also years ago I recall visiting Tarcisio Bettinsoli and he had a lot of similar actioned doubles ready for delivery.
It is a simple action, engineered for simplicity. The one visible pin on the action body holds the trigger plate. There are no screws on this gun, everything is pinned. The double underlugs do just fine with no middle bridge on the action and obviously no "fitting on the circle" of the rear lump, as there is none. All these simplifications bring down costs. To the makers credit, simplification is combined with high quality finish and the result is, I think, a good deal.
Engineeringtech, had it been my gun, I would have put in a coil spring that fit and gave the preload that felt right for the job. Not blaming you, but coil springs are far more adaptable than V springs. As for the other details, they are pretty appaling.
